What's up with CoreStats.Parent editability in versions > 26.05? Is this a bug?

Summary: Working on regression testing for patching up to 26.07, we're seeing unexpected changes in the editability of the CoreStats.Parent property. See the screenshot—left side is our production application (26.05), right is our regression testing application (26.07). Additionally, we're unable to toggle the "Editable" parameter at all (i.e. it's not just that the setting changed mysteriously, it's that I cannot fix it). Note: we skipped 26.06 (hence the version gap), but we see this same phenomenon in 26.06. We first noticed it as a new warning appeared in a Node Type Converter (see 2nd screenshot).

Is anyone else seeing this?

Content: The applications in the screen captures below are exact clones, the only difference is their patch version.